Narrative:

While at cruise at FL370; during 2nd half of second bathroom break; PNF became aware of a lack of O2 pressure from his mask. Gauge on overhead indicated near zero. Conferred with dispatch (weather and fuel burn); maintenance and fom and descended to FL250. We positioned a therapeutic O2 tank on flight deck with 2 masks unwrapped and ready to use and continued to our destination without further problems. Did not hear the result from maintenance but assume an oxygen leak.

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Original NASA ASRS Text

Title: During cruise flight the B737-800 Captain noticed no oxygen in his mask while the First Officer was on a physiological break; and; assuming a leak; had a cabin supplemental bottle and two masks brought to the flight station and descended to FL250.

Narrative: While at cruise at FL370; during 2nd half of second bathroom break; PNF became aware of a lack of O2 pressure from his mask. Gauge on overhead indicated near zero. Conferred with Dispatch (weather and fuel burn); Maintenance and FOM and descended to FL250. We positioned a therapeutic O2 tank on flight deck with 2 masks unwrapped and ready to use and continued to our destination without further problems. Did not hear the result from Maintenance but assume an oxygen leak.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.